heeeeeeelp!

[stephen1990]

Right folks, I have a strange problem with my megane, it started a few weeks ago with the water temp gauge rocketing to 3 bars as soon as the engine is turned on (even if I haven't drove it all day) and then gradually drops down to say 2 and a half bars, its hammering my petrol consumption too and sometimes petrol odours come through the vents which is worrying because my stepson who has problems with his lungs has just come out of hospital and wouldn't like to see him go back in because of my car, if I have the vents turned to 0 they still get hot, its really worrying me and getting on my nerves, any idea what it could be?

[Keyholder]

have u checked for headgasket failure??

Check for fumes coming out of the coolant tank or oily residue. check your oil filler cap for a mayo type substance, Have you notcied a loss in coolant ? oil level dropped ? some over heating issues can cause a poor mpg, common on rovers.

Have you flushed youre coolant system out making sure its free from crap / rust / sludge build up etc.

[stephen1990]

At first I thought it was the sender unit failure when I looked in the haynes manual, I'll have to check it when I've got more time

[davelowe]

I've been thinking about this problem for about 15 minutes and have nothing of value to add.

It seems you have two problems, one with the cooling system, and one about petrol vapours.

How they interrelate is puzzling. The temperature gauge should not register hot when it is cold. If the ECU were to receive such an indication, it would make the mixture leaner, so this is at odds with the fumes. When driving, the temperature gauge decreases. Why? The fact that the temperature at the vents is hot might point in the direction of the thermostat - or an airlock preventing the radiator from functioning properly. But this does not explain the gauge...

As for the petrol fumes, I simply don't know. Check all the basics with the car stood on the driveway. Observe the fans, temperature and so forth. Also - get any codes read.

I'd really like to know how you solved this - it would be educating.

[stephen1990]

Well I've been pondering it myself and still think it could be a gasket, I did do checks when the car was on the drive, the fan wasn't moving but this gauge problems doing my nut in, I filled up £71 in petrol on saturday and that usually lasts me 2-3 weeks but now its hit halfway and I've barely been driving anywhere, so could be a gasket and petrols leaking out somewhere, the water levels fine, engine oil levels fine as indicated on the dashboard when the cars started, what's really puzzling is that I have the heaters off yet it still heats up!

When I was stuck in that bloody storm on thursday my windows steamed up and had to risk the fumes and turn the heaters on low heat on 1 (for 3 hours) my mpg has dropped to 31.6mpg. My colleagues son in law is a grease monkey and is going to look at it tonight before I start work, fingers crossed its just a gasket because they are pretty cheap to replace (£33 on carparts4less.co.uk). could it not have something to do with the sender unit possibly thermostat?

[stephen1990]

have u checked for headgasket failure??

Check for fumes coming out of the coolant tank or oily residue. check your oil filler cap for a mayo type substance, Have you notcied a loss in coolant ? oil level dropped ? some over heating issues can cause a poor mpg, common on rovers.

Have you flushed youre coolant system out making sure its free from crap / rust / sludge build up etc.

Now you mention it my coolant levels did used to drop dramatically

[tomalamix]

well, with all that symptoms make a pressure test to the cooling circuit. when you apply pressure to the circuit it must not drop, if it does it means the coolant is going somewhere...

another test is to check the pressure value inside the circuit after the car is warm, it must not reach a cartain value (i really dont know the threshold).

if in any of both cases you have problems it means your gasket is caput ..

[stephen1990]

Well the mechanics been to inspect the car and has ruled out the gasket as the cooling system is fine and has come to the conclusion its the coil packs, one of them has completely shut down when he was testing them and is now on 3 cylinders and has advised me to drive it as little as possible, £60 to replace two packs which aint bad, if it was the gasket that went it wouldve been £367 excluding labour!

[davelowe]

Result with a caveat: the unburned fuel will f**k the catalytic converter. Don't move the thing until you have it repaired.

How you didn't spot 3 cylinders is a mystery!!

[stephen1990]

Has to be driven home from work in the morning, sooner 6am comes the better, its getting fixed monday, It all makes sense now though because I do believe the coil pack and the seal on my back box are linked. With this being my first car I am inexperienced with the noises and other things so this is a (expensive) learning curve for me with this megane.

[tomalamix]

that doesnt explain the water disappearing...

[stephen1990]

He couldn't see anything wrong with the cooling system, but its still a mystery, I might have a leak somewhere and will have to be investigated

[stephen1990]

Well changing the coil packs did nothing! The problems still there! Booked into the garage for a diagnostics test next week

[davelowe]

The coolant could simply have boiled off owing to overheating.

Getting the codes read is definitely the right idea.

[stephen1990]

Still doesn't explain how its destroying my fuel